A drone is a flying machine that is remotely piloted by means of a control device. Certain drones are said to be rotary-wind drones, which covers all types of scale models of known helicopters.
WO 2008/056051 A2 (Parrot) describes a game system using remotely-controlled toys, in particular remotely-controlled drones. The game is performed by piloting the drone on site, e.g. around a virtual circuit with the image of the circuit being superposed on the real image picked up by the camera of the drone. Virtual passing points are defined through which the drone must pass, and they are displayed, for example, in the form of virtual rings floating in the air.
As can be understood, in such a game it is necessary to be able to pilot the drone very accurately. The same applies to chase games in which a drone piloted by one player seeks to shoot down a stationary or moving target, for example a drone piloted by another player.
Until now, a drone has been piloted from a radio-control unit having two movable levers, in which:                for the first lever, a first axis controls pitching of the drone (in one direction to move forwards, or in the opposite direction to move backwards), while a second axis controls pivoting of the drone (tilting the lever in one direction to pivot to the left and in the opposite direction to pivot to the right); and        for the second lever, a first axis controls the driving power of the drone (in one direction to increase the power and in the opposite direction to reduce it), while a second axis controls roll (in one direction to move crab-wise to one side and in the other direction to move crab-wise to the opposite side).        
Specifically, learning to use the controls takes a long time and requires a great deal of practice, while running the risk of damaging the drone during the learning stage.
As a replacement for those levers, or in combination with them, it is also known to make use of buttons for piloting a drone.
US 2005/0048918 describes a control device for such a drone, specifically a miniature dirigible balloon, by using a control device of the portable telephone type. Key presses on the telephone are detected and transformed into commands for piloting the dirigible: accelerating or slowing down its drive, pivoting its rudder, etc. Simultaneously, a camera on board the dirigible picks up an image that is transmitted to the telephone and displayed on its screen.
A drone with a self-contained stabilizer system is described for example in WO 2009/109711 A2 (Parrot).
This type of drone is particularly suitable for inexperienced people who find it difficult to stabilize a rotary-wing drone using conventional lever controls operating the throttles, rolling, pitching, and yawing in more or less simultaneous and interdependent manner. These difficulties are often made worse when flying a radio-controlled scale model since the user has no force return and must therefore make do with seeing the machine and assessing its position in three-dimensional space, which requires a very good knowledge of the physics of flight in order to be able to interpret the position and understand what actions need to be undertaken in order to reach an equilibrium point.
The above-mentioned document describes a drone that is provided with automatic means for stabilizing the drone in hovering flight and serving in particular, once an equilibrium point has been reached, to provide the corrections that are needed to maintain such a stationary point by “trimming”, i.e. by making numerous small corrections of variations in translation due to external effects, such as movement of the air and drifts of the sensors.
When automatically stabilized in hovering flight in self-contained manner, such as a drone thus enables people inexperienced in piloting, and in particular children, nevertheless to be able to pilot the rotary-wing drone without needing to act directly on traditional flight controls, but instead to take advantage of intuitive piloting based on horizontal and vertical movements. The dynamic movement of the drone is thus transformed into movement between successive equilibrium points by simple commands such as climb, descend, turn left or right, move forwards or backwards, etc., each command being associated with a particular button of the remote control housing. When the user releases all of the buttons, then the drone automatically returns to hovering flight, in the new position that it has reached.
Numerous devices are known that include tilt sensors, in particular portable telephones. WO 2005/027550 A1 (Nokia Corporation) describes such a portable telephone provided with means that enable the tilt of the telephone relative to the horizontal to be detected about two orthogonal axes.
WO 01/43473 A1 (Telbird Ltd.) describes how to use a telephone for remote control of various actions, e.g. moving a cursor through text displayed on a screen.